tone bank on casio sa-21 wont sound

[Pieter]

hello circuitbenders forum,
glad to have found you! Here is my first issue, last week i found a casio SA-21 100 sound tone bank. I tested  it at the shop; rhythm accomp. volume, demos, 5 percussion pads, and the tone bank worked fine.  Somehow between the second hand shop and my flat it lost all these features.  I am still confident that i can recuperate what has been lost but i dont know what to look for or where to test and what to do once i find the problem.  Nothing looks broken or burnt however the ON/OFF contact is a little blackened so i will get  contact cleaner. . .  while poking around i managed to get the chopin demo to play.  But I am a little lost.  any advice would be greatly appreciated,

                                                                                                                       thanks

                                                                                                                                   pieter

[computer at sea]

The power switches in those SA keyboards are terrible.  I'd give that area a thorough check.